The implications of memory-magic/A magic usable for an unthinkable weapon?

There seems to be an element in the recent stories that strikes me as quite... unusual for a fantasy setting. Not exactly the matter THAT it occurs but the fact that we have had it so often. What I am talking about here is memory-magic, what we could see both in Garen's story and in Ahri's stories.

The tl,dr: memories can be stolen and/or absorbed, the person affected will often not notice anything missing by themselves, unless it would change their entire character over. Potentially it might even be possible to even IMPLANT FAKE MEMORIES. Seriously we're gonna go full sci-fi here at some point, and this would be too good of a story-idea to pass up for the writers, so we will see one like that in the future, probably in Zaun as that fits the "dark sci-fi vibes" of it.

But what worries me more is the existence of said magic in a world that was in a state of a constant magical world-war for most of its existence. Especially when you had world-runes clashing entire landscapes were changed overnight, even more so when people truly knowing what they were doing were using them. So using magic for war is the absolutely normal thing in this world.

However, what if you don't need to even fight the war? What if you could make all the enemy soldiers and civilians just FORGET THEIR OWN COUNTRY AND THE CLAIMS TO THEIR LAND? What if they would suddenly forget their entire ideology and culture? What if you could literally wipe out your own crimes from human history? What if you can plunder and pillage an entire nation, then use the mind wipe and no one will ever remember you were there or notice that something was even stolen, swear revenge or come after you? How could they ever prepare against a foe no one can remember to have ever fought against?

What I am talking about here is a powerful magical method to make the memory-drain into a crude-but-potent area-of-effect weapon.

And as we already know: people usually dont know when memories are stolen, especially when no one else remembers a single thing either. Entire kingdoms might have gotten "deleted" out of the Runeterran history at this point, and I am not sure if Bard would even intervene. He only comes when the fabric of reality is endangered, not when mankind screws itself over with "normal" magic once again.

Also: memories gotta go somewhere. Usually you have the drained and someone absorbing, either a person or the plants in Ahri's garden story. So is there in the world an entity or an artifact that holds the fragmented memories of potentially millions of people? What could you do with that? How powerful would that be if it was converted into raw magical power? Given that witches seem to draw them out for their own powers this convertion seems possible after all.

So somewhere in Runeterra there might be an artifact or being powerful enough to potentially blow up the entire world - or at least make a dent so massive everyone's gonna notice. And the worst part: there is no way to disprove this theory, because the point of the mind-drain is that no one remembers a darn thing.

I'm seriously curious how this story will go, also when looking at the whole "steal memories -> implant fakes" kinda thing.